The iontophoresis is a method of delivering into a living organism a component such as an ionic medical agent useful for a living organism by using, what is called, an electrophoresis. This is also called as an ion transfer therapy, or an iontophoresis therapy, and is mainly used for a systemic drug administration.
The iontophoresis apparatus generally comprises a structure of electrode for an operation holding a pharmaceutical solution wherein the medicinal components (physiologically active substances) are dissociated into a positive ion or a negative ion (drug ion), a structure for a non-operation playing a rule for a counter electrode of the structure of electrode for an operation. The drug ions are administered into the living organism by adding the same polar voltage as the drug ions to the structure of electrode for an operation through the electric power unit under the condition that these both structures are in contact with the skin of the living organism (human or mammal). In rare cases, to both structures may be included the physiologically active substances, and the both electrodes may be a structure for an operation.
In the meantime, intra-articular administration of a water-soluble steroid is carried out as an injectable solution in the medical treatment of rheumatoid arthritis and arthrosis deformans etc. However, the mode of injection brings on pain when it is administered, so that an advanced technique by a medical doctor is required. Further, these are not absolutely a simple, safe, secure and highly available administering method in the medical drug field, since these medical treatment may lead to the infectious diseases from the site of administration.
In order to solve the above problems, it is known the dermal administration of dexamethasone sodium phosphate which is one of the water-soluble steroid by using a direct-current type of the iontophoresis (Nonpatent literature 1).